Transmission of sound and images



July 25, 1933. M. RYAN TRANSMISSION OF SOUND AND IMAGES Filed April 19 4770/?NEV Patented July 25, 1933 UNITED STATES PATENT OFFICE "F ANoIs M. YAN, or EAST ORANGE. NEW anRsEY, AssIGNoR To BELL TELEPHONE LABORATORIES, INCORPORATED, or NEW Y RK, N. Y., A CORPORATION OF NEW YORK I Application filed April 19,

This invention relates to the art of electrical communication and has for an object the simultaneous transmission of an image of a distant speakerand of his speech in an eflicient and economical manneri Television, that is, the transmissionto' a remote point of anfimage of a distant object or scene is based upon the analysis of the remote scene point-by point in a time sequence and'the transmission of energy varying according to-the variations from point-to-point of the light and shade characteristic Of the scene. The transmitted energy is then utilized to control at a receivreconstructed image, the image being formed point-by-point in a. time sequence corresponding to that of the analysis of the remote scene which is being scanned at the transmitting station. This requires at the transmitting station apparatus capable of analyzing point-by-point the scene to be transmitted and producing energy which varies correspondingly. It requires at the receiving station apparatus capable of reproducing an image point-by-point and for converting the received transmitted energy into variations of light with which to illumine the successive points. It further requires that the scanning apparatus at the transmitting station and the image reproducing ap-j paratus at the receiving station be held in close synchronism and isochronism, so that for each point in the scene at the transmitting station there will be in the image produced at the receiving station a point corresponding not only in position but also in its illumination or light and shade characteristics. In order to produce the impression of a single continuous image the phenomenon of persistence of vision is brought into play. It is only necessary that the image at the receiving station be formed at least asfreorder to create the illusion that the image is continuous with respect to time. Although 1 of course, be understood that the points are ing pointthe building up or formation of a;

quently as 16 or more times per second in TRANSMISSION' OF SOUND- AND IMAGES 1927. Serial No. 185,028.

in' fact elemental areas which maybe of any. desired size depending upon the desired degree of detail and the requisite faithfulness to the Original of the likeness or image to be reproduced. Such a system is briefly described at page 1 of the New York Times published April 8, 1927.

According tothe present invention a television-system is combined with a telephone system in such manner'as to permit one to Q both see and converse with a person at a remote point. This is accomplished by cans ing the speech or sound waves at the remote point to modulate an intermediate carrier frequency wave so that the resulting modulated waves will occupy a frequency range above that occupied by the image forming currents. The modulated intermediate fre 'quency carrier waves and the image-forming currents are then caused tosimultaneously Q modulate a principal carrier of frequency suitable for radiotransmission. Atthe receiving station the incoming energy is received and detected to separately reproduce speech currents and image forming currents 5 correspondingto those produced at the transmitting station; The speech currents operate the telephone receiver and theimage forming currents control reproduction of the image. p

The novel features which are considered characteristic of the invention are pointed out with particularity in the appended claims. The inventionitself, however, both as to details of its organization and its mode 8 of operation will be best understood by reference to the following description taken in connection with the accompanying drawing which illustrates a combinedtelephone and television system designedto permit a person at station A to see and conversewith another person at a remote station B. The scanning apparatus of the television system may consist of a perforated rotating disc which permits pencils 'oflight froma source of. light of great intensity to sweep the objectt'in this case the countenance of the person at station B) in successive arcs and thus to traverse substantially'its entire area; At any partlcular instant, a beam or pencil of light incident upon the object strikes that object at a definite point or elemental area and the light reflected by the object depends upon the reflecting power of that particular point or elemental area upon which the beam or pencil is incident. One or more photoelectric cells so placed as to be screened from light except that reflected fromthe object will accordingly respond to variations in the reflected light to yield a varying electric current which may be transmitted to the distant point to reproduce an image. At the receiving station these image-forming currents may be caused to control the instantaneous illuminationof a de-. vice such as a neon lamp. perforated disc apparatus similar to that used at the trans mitter may be placedin frontof the neon -lam). An observer view in the disc will see successive portions of the neon tube point-by-point in a time sequence and as the illumination from the tube is rising and falling in consonancewith the reflected light at the transmitting station the observer will see an image of the distant object. Such a system is disclosed and claimed in application Serial No. 227,649,; filed October 21, 1927, F. Gray.

' The scannin and ima e re )roducin a i h b b paratus may beheld in synchronisni by any suitable means. An example of such apparatus is diclosed and claimed in U. S. Patent 1,763,909, issued June 17, 1930, to H. M.

- Stoller-E. R. Morton.

It is apparent that the variations'in the image current energy transmitted will have a frequency of'greater or less range depending upon the total area of the image which it is desired to reproduce, the number j of tunes per second in which it is to be scanned,

and the area ofthe elemental points. 'It has been found that satisfactory pictures maybe transmitted using a frequency transmission range of from about 10' to about 45 20,000 cycles per second. In other words, the energy to be transmitted, which varies irregularlyin accordance with the lights and shadows of the image as it is analyzed from p0int-to-point, consists of essential elemental componcnts ranging from substantially zero to substantially 20,000 cycles per second.

Speech sounds, as is well known, comprise an essential range of from approximately 0 to 3,000 cycles and in the case of high quality speech or music it is frequently desirable to use a much broader range eX- tending up to 5,000 or 6,000 cycles or even more. In addition to the energy for reprothe so-called voice frequency range. It will accordingly be apparent that the energy for transmitting the image and that for transmitting the speech will lie in frequency bands which overlap. One of the principal objects of this invention is to enable transmissionof these energies over a single channel as for example by means of a single radio transmitter.

Referring to the drawing the person at station B is shown facing a scanning disc 1 behindv which is a source 2 of intense light, a pencil or beam from which passes through the perforated disc and is reflected from the face of the speaker at that station upon one or more photoelectric cells 3. A driving motor lis provided with a shaft"oirwhich the disc 1 is mounted and causes the light pencils through the disc to completely scanjthe speaker at least 16 times per second. Accordingly photoelectric cell 3 sets up in its circuit currents having compenents of frequencies rangingfrom practicallv zero to over 20,000 cycles per second.-

rents'from the photoelectric cell 8 trans mitted through the selective circuit 9 and the speech modulated wave and image currents accordingly modulate the radio carrier wave (C) supplied by'oscillator 10. The radio carrier wave modulated by both speech and image forming currents is radia ted from antenna 11. It will be understood that suitable amplifiers are provided wherever desirable and'particulm'ly in the circuit associated with the output of the photoelectric cell The motor 4 at station B so designed that its normal speed is approximately that required to hold disc 1 in synchronism with the corresponding. disc'at station A. A synchronizing device 12 operated by energy from radio receiver 13 holds the motor in exact synchronism with that at station A.

For simplicity of illustration a wire, circuit is indicated connecting the microphone circuit at station A to the speech receiver 14 at station B.

The wave radiated from the transmitting station comprises vseparate groups of components, two of which represent speech 1nod ulated waves and a third a carrier wave modulated by image currents.

- The receiving station comprises two re-' ceivers, one selective of one group of comthe detector to produce the speech cur rents which are supplied to the telephone re-v ceiver 15 used 'bytheobserver at the 'receiving'station. 7

At the second radio receiver the incoming \vave'carrying the image currents is combined with ,locally supplied oscillations in the demodulatorlti to produce an image current modulated wave of frequency different from the transmitted carrier, Which is selected by the filteri17. The selected Wave is combined with oscillations supplied by a local source 17 to produce an image current modulated Wave. This wave is selected byithehfilter 18 anddetected in the detector 19 to yield the image currents which are selected by the filter 20 and supplied to production of the image. M

\Vherever desirable amplifiers may be used, and such amplifiers maybe three-electrode space discharge tubes. t Byway of example, the following frequencieswere used atthe trai'ismitting station, the carrier. Wave carryingthespeech modulation was kilocycles, the radio carthe neon lamp 21 for controlling the re-;

- rier Wave 1575 kilocycles, and as a result the outgoing Wave consistedof three groups ofcomponents based on 1545. k11ocycles,j 1575 kilocycles, and 1605 kilocycles.

The radioreceivcr for the speech modulatcd Wave was selective ofthe Wave based on 154-5 kilocycles and the locally supplied oscillations were 1462 kilocycles, the intei medlate frequency wave being 83k locycles. Thereceiverfor the image-current modu lated Wave was tuned to select the wave based on 1575 kilocycles and the frequency of the locally suppliedoscillations combined with this wave was 3545 kilocycles, and resulted in a modulated Wave based on 5120 kilocycles, This wave was combined with speaker at a transmitting station, simulta neously producing other electric currents having a characteristic variation corresponding to his speech, simultaneously modulating the same carrier Wave With both of said current variations in a manner such that the fre:

quency bands covered by the respective modulations occupy different positions in the frequency spectrum and utilizing said Wave at the receiving station in the production of an image of the speaker and in the reproduction of his speech so that an observer thereat may simultaneously see and hear said speaker-at the transmitting station.

2. A communication system comprising means at a transmitting station for scanning the face'of a speaker point by point, current controlling means for simultaneously receiving the voice of said speaker, means controlledrbysaid scanning means for produc= ingelectric current variations corresponding to the appearance of said speaker, means controlledby said voice operated means for setting up current variations corresponding to the voice of said. speaker, means for causing both'said variations to simultaneously modulatet-he same carrier Wave ina manner such that the frequency bands covered by of the face of said speaker, means at said rev ceivmg. station controlled by said carrier current} for-reproducing the voice of said speaker, and means independent of sald car-.

rier for maintaining .the'scanning means at 1 the transmitting station and said image producing means at the receiving station in ex-.

act synchronism.

8. An electric communication system for enabling a person at a receiving station to both see and hear a person at a distant transmitting station by means of speech and image variations carried by the samehigh frequency carrler Wave, transmitted from .the one station to the other, as modulations such that the frequency bands covered by the respective modulations occupy different positions in the frequency spectrun'i, com-' prising means for. receiving said carrier wave and for obtaining, therefrom low '1'requency speech and image variations like the originals at the transmitting station and each entirely separate from the other, means for impressing the speech variations upon a sound producing device, and means controlled by said image currents for setting up an image offthe distant field of vlew.

41. In a televis on andsound transmission system having the signals confined Within a continuous frequency band, means for producing and transmitting television signals groupedabout a predetermined carrier frequency and occupying a relatively large portion of the frequency band, and means for simultaneously producing and transmitting related sound signals grouped about a'sec- 0nd predetermined sound carrier frequency separated from the television carrier and adjacent thereto and ar anged to occupy a relatively small portion of the said" fre quency band.

5. In a television and sound transmission system having the signals confined Within a continuous frequency band, means for producing and transmitting television signals grouped about a predetermined carrier frequency and occupying a relatively large portion of the frequency band, means for simultaneously producing variations correspond ing to related sound signals, means for producing a carrier current oflower frequency than said first mentioned carrier and for modulating said carrier current with said sound signals, and means for modulating said first mentioned carrier With said sound modulated current in a manner such that the resultant n'iodulation produced by the sound signals lies external to the frequency baud covered by the television signals and adjacent thereto and arranged to occupy a relatively small portion of the said frequency band. A I

6. In a television and sound transmission system having the signals confined Within a. continuous frequency band,means for producing and transmitting television signals grouped about a predetermined carrier frequency and occupying a relatively large portion of the frequency band','means for simultaneously producingvariations corresponding to related sound signals, means for producing a carrier current of lower frequency than said first mentioned carrier and for modulating said carrier current Withsaid sound signals, means for modulating said first mentioned carrier With said sound modulated,

current in a manner such that the resulting modulation produced bythe sound signals lies external to the frequency band covered by the television signals and adjacent thereto and arranged to occupy a relatively small portion of the said frequency band, means for receiving said continuous band and for obtaining therefrom low frequency sound and television signals like the originals at the transmitting station and each entirely separate from the other, means for impressing the sound signals upon a sound produc ing device, and means controlled by said television signals for setting up an image of the distant field of view.

7. In an electric communication system for transmitting television and sound signals by means of speech and image variations carried by the same high frequency carrier wave modulated by speech and image variations in a manner such that the frequency bands covered by the respective modulations occupy mutually exclusive but adjacent positions in the frequency spectrum, means for receiving said high frequency Wave and for obtaining therefrom low frequency sound and image variations like the originals at the transmitting station and each entirely separate from the other, means for lmpressing the sound variations upon a sound producing device, and means controlled by said image variations for setting up an image of the distant field of View.

8. An electric communication system for enabling a person at a receiving station to both see and hear a person at a distant transmitting station by means of a high frequency carrier Wave modulated by speech and in'iage variations in a manner such that the frequency bands covered by the respective modulations occupy mutuallyexclusive positions in the frequency spectrum comprising means for receiving said carrier Wave and for obtaining therefrom low frequency speech and image variations like the originals at the transmitting station and each entirely separate from the other, means for impressing the speech variations upon a sound producing device, and means controlled by said image currents for setting up an image of the distant field of View.

9. An electric communication system for enabling a person at a receiving station to both see and hear a person at a distant transmitting station by means of. a high frequency carrier Wave modulated by speech and image variations in a manner such that the frequency bands covered by the respective modulations occupy mutually exclusive positions in the frequency spectrum comprising means for receiving said carrier Wave and for obtaining therefrom low frequency speech and image variations like the originals at the transmitting station and each entirely separate from the other, Which includes means for separating said sound and image modulations, means for reproducing said sound variations, means for stepping up the frequency of said image modulation and for selecting one of the modulation products resulting therefrom, means for stepping-clown the frequency of said selected product and selecting one ofthe modulation products resulting therefrom, and means for detecting the last mentioned selected modu lation product to produce the'image variations, means for impressii'ig the speech variations'upon a sound producing'device, and means controlled by said image currents for set-ting up an image of the distant field of view.

10. In a television and sound transmission system having the signals confined within a continuous frequency band, means for producing and transmitting television signals grouped about a predetermined carrier frequency and occupying a relatively large portion of the frequency band, means for simultaneously producing variations corresponding to related sound signals, means for producing a carrier current of lower frequency than sald first mentioned carrier and for modulating said carrier current with said sound signals, means for modulating image modulations; means for reproducing sald sound variatlons, means for stepplng up the frequency of said image modulationand for selecting one of the modulation products resulting therefrom, means for stepping-down the frequency of said selected 7 product and selecting one of the modulation.

products resulting therefrom, and means for detecting the last mentioned selected modu-' lation product to produce the image Variations, means for impressing the speech variations'upon a sound producing device, and means controlled by said televisionsignals for setting up an image of the distant field of View. s

FRANCIS M. RYAN. 

